Liquid level measuring apparatus



M. K. RICHARDS 2,486,207 LIQUID LEVEL MEASURING APPARATUS Filed Aug. 11, 1945 Melbourne K. Pic/mrals $.3 M a M a possibility of introducing sufiicient of the conabsorbent is an alkali-metal chloride or an altures. Because of the corrosiveness of the chemin ingmetal fluoride and gaseous chlorine. The

tailed description of the invention. applied to a cell for the electrolytic generation of Patentedt25 I 2,486,207

UNITED s'rAgrss PATENT," OFFICE LIQUID LEVEL MEASURING APPARATUS Melbourne K. Richards, Wilmington, DeL, assigner to the United States oi America as represented by the United States Atomic Energy Commision Application August 11, 1945, Serial No. 610,349

2 Claims. (Cl. 73-302) This invention relates to the measurement of sure and the difierence between the pressure of liquid levels in closed containers and is particuthe gas feed and that of each of the'gas spaces larly concerned with the measurement of liquid constitutes a direct measure of the height of the levels in a container havingtwo or more gas liquid column from the gas feed to the liquid compartments above the same body of liquid. 5 level in that particular compartment.

The invention is of particular importance in the The gas feed may be made up of any suitable electrolytic generation of fluorine by the elecinert gas which is not objectionable in the final trolysis of anhydrous acid potassium fluoride product. Thus one of the ga'sesgenerated may electrolytes. Cells for the production of fluorine be employed and introduced into the correspond normally comprise an anode compartment and ing compartment of the generator. If a small a cathode compartment for the separate collecdegree of dilution is not objectionable, another tion of fluorine and hydrogen'generated by the inert gas, such as nitrogen, helium, or argon, electrolysis. It is obviously desirable to know the may be used. The inert gas is introduced at a liquid levels in the compartments of such fluorine sufficiently low rate to provide no substantial cells in order to regulate the addition of electropressure drop between the manomter connection lyte. Moreover, it is important that the pressures and the outlet beneath the liquid in the container. in the two compartments be controlled to prevent In the measurement of electrolyte levels in excessive rise or fall of the liquid level in either fluorine cells, the manometers may be provided compartment. An excessive rise in the liquid'level with a liquid inert to elemental fluorine and hymay result in carry over of the electrolyte into drogen fluoride; for example-a high boiling flusubsequent gas treatment apparatus, whereas too orocarbon may be used. However the use of such great a drop in the level may permit gas to pass relatively costly materials may be avoided by inirom one compartment to the other with a resultterposing between the manometer and the gas ant introduction of fluorine. While such concompartments an absorber for the removal of tamination is undesirable in any event, there is elemental fluorine. A most satisfactory type of taminating gas to produce anexplosive mixture kaline earth metal chloride such as sodium chlowith the hazardous consequences which may re-- ride or calcium chloride. Any fluorine passing suit from the unsuspected handling of such mixinto this absorbent reacts to form the correspond-- cals involved, materials permitting direct obsermanometer liquid then may be any material not 1 vation of liquid levels cannot be employed and readily attacked by chlorine or hydrogen fluoride mechanical and electrical measuring instruments 1 vaporat normal temperatures. Liquids such asare apt to become inaccurate. tricresyl phosphate, pentachlorethane, or 1,2,4- It is an object of the invention to provide a trichlorobenzene containing du Pont Oil Red to simple means for measuring liquid levels in .ves improve visibility have served efiectively. The sels containing two gas compartments above the useof an absorbent between the manometers and same body of liquid. Afurther objectistoaccomthe gasspaces of the containing vessel has the plishthis measurement by a gas bubbler of simple further advantage that the lines connecting the structure. A further object is to provide a liquid absorbers and manometers will be free of fluorine, level measurement apparatus suitable for appli- 40 and by locating the absorbers close to the cell and cationinsystems involving highly corrosive matethe manometers a substantial distance away, rials such as the fluorine, hydrogen fluoride, and danger to the operators, as a result of possible acid potassium fluoride electrolyte involved in leakage of fluorine, is substantially reduced. the electrolytic production of fluorine. Still fur- In the attached drawing one embodiment of ther objects will appear from the following dethe invention is illustrated diagrammatically as In accordance with the invention the gas comfluorine. The numeral I designates the container partments in which liquid levels are to be measfor electrolyte. This container is closed by a med are connected to manometers which are in cover '2 from which a bell 3 depends to form' a turn connected to a gas feed to the body of liquid central fluorine space and an annular hydrogen beneath the compartments. The manometers space. Whether the container i is of cylindrical thus measure the difference in pressure between or rectangular cross-section is of no consequence the gas spaces and the gas feed. Since the same as far as the present invention is concerned as liquid body is beneath both gas spaces, the liquid the invention is equally applicable to both types level in each space corresponds to the gas presof cell. Perforated partitions or diaphragms 4 the anode chamber and the spaces and the walls of the cathode chambers.

1 Anode and cathode structures and other conventional items have been omitted Irom the drawing for the sake of simplicity since they form no part of the invention. The top 2 of the cell is provided with a fluorine oil-take pipe and a hydrogen oil-take pipe 8. heading into the cathode compartment is an inert gas conduit I having its outlet at any desired normal electrolyte level and connected with a flowmeter 8, illustrated as a simple visible bubblecounter fed by an inert gas supply line 9. Connecte'd across oil-take pipe and gas conduit I is a manometer which is protected by an absorber ii. Connected across hydrogen oil-take 6 and conduit 1 is a second manometer I2, protected by an absorber IS. A scale it is provided for reading the manometers.

If desired, a differential pressure gauge i5 measuring the difference between line pressure and atmospheric pressure may be provided between manometer i2 and absorber l3 or, alternatively, between manometer l0 and absorber ii, or both, for indicating the pressures on lines 5 and 6 directly.

The measuring device illustrated may be calibrated as follows:

With electrolyte in the container at a known level above the outlet of conduit 1, and with gas oil-takes 5 and 6 at atmospheric pressure, nitrogen or hydrogen is introduced at a low constant rate as indicated by the flowmeter 8. The pressure readings on manometers l0 and I! are indicated on the scale It. The electrolyte is then raised to approximately the maximum level to which it may rise during operation and a second reading on manometers l0 and I2 is taken and marked on the scale. Between these limits the height of the electrolyte will be proportional to the manometer scale reading and the scale can be graduated accordingly. An alternative method of calibration involves determining a single electrolyte level scale reading and computing other electrolyte level'scale readings on the basis of the known densities of the electrolyte and the manometer liquid. When the electrolyte level is maintained by intermittent additions of hydrogen fluoride, a slight calibration error is introduced because of the change in density of the electrolyte. In most operations this error is not significant. If desired, it can be accounted for by a correcting factor based on the average level indicated by the manometers. In the practical application of the system this has never been necessary as sufficient accuracy for control purposes is secured without it.

When the apparatus has been calibrated, it is ready for operation. In order to determine any variation in the liquid levels in the anode and cathode compartments, it is merely necessary to diaphragm! I and point below the minimum note the difference between the readings of manometers I0 and i2. When manometer I! gives a higher reading than manometer I0, it shows that the liquid level-is higher in the cathode compartment by a corresponding amount.

While the apparatus has been described with particular reference to its application to electrolyte level measurement in a fluorine generator, it is to be understood that the invention is not intended to be so limited since it is applicable to any liquid level measurement in containers involving two or more gas compartments above a single body of liquid and that it is particularly advantageous in situations involving chemicals which preclude the efllcient operation of ordinary indicating devices. It will be understood further that I intend to include variations and modifications of the invention and that the preceding example is illustrative only and in no wise to be construed as a limitation upon the invention, the scope of which is defined in the appended claims, wherein a I claim:

1. A liquid level measuring apparatus for an electrolytic fluorine cell comprising an anode compartment and a cathode compartment separated by a perforated partition and having separate fluorine and hydrogen collecting spaces, said apparatus comprising an inert gas inlet for introducing an inert gas into the cathode compartment substantially below the normal electrolyte level, a manometer connected across the inert gas inlet and the fluorine collecting space, a second manometer connected across the inert gas inlet and the hydrogen collecting space, said manometers containing a liquid inert to chlorine, and a pair of fluorine absorption tubes containing a chloride fluorine-absorbent, one of said absorption tubes being connected between each of said manometers and the respective collecting space.

2. A liquid level measuring apparatus for a fluid container having a plurality of gas spaces closed at the bottom by a single body of liquid, said apparatus comprising a gas inlet for introducing an inert gas into the body of liquid below one of said spaces substantially below the normal liquid level, and a separate manometer connected between the inert gas inlet and each of said spaces.

MELBOURNE K. RICHARDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

